Preparation of phosphinodithioic acid anhydrides by heating the corresponding acids



United States Patefit ice PREPARATION OF PHOSPHINODI'I 'HIOIC ACID ANHYDRIDES BY HEATING THE CORRESPOND- ING ACIDS Willis G. Craig, Willoughby, and Clark 0. Miller, Cleveland, Ohio, assignors to The Lubrizol Corporation, Wickliife, Ohio, a corporation of Ohio N Drawing. Application January 26 1954,

Serial No. 406,325

7 Claims. (Cl. 260-545) This invention relates as indicated to anhydrides" of phosphinodithioic (dithiophosphinic) acids and more particularly to a process for the preparation of said anhydrides.

The term phosphinodithioic acid as used herein refers to a molecule which conforms to the structural formula:

wherein R and R are the same or diiferent organic radicals attached to phosphorus through a carbon atom, preferably hydrocarbon radicals from 1 to carbon'atoms, especially cyclic hydrocarbon radicals, and most desirably aryl radicals. In the following table are given examples of R and R in the above formula:

TABLE (1) Aliphatic radicals, for example:

Alkyl radicals, e. g.:

Methyl Ethyl Propyl (nand iso-) V Butyl (11-, sec-, iso-, and tcrt-) Amyl (11-, sec-, iso-, and tert-) Hexyl radicals, e. g.: n-Hexyl Sec-hexyl 2,2-dimethyl-3-butyl 2,2-dimethyl-4 butyl 2,3-dimethyl-2-butyl Z-methyl-l-pentyl 2-n1ethyl-2pentyl 3-methyl-1-pentyl 3-methyl-2-penty1, etc.

Heptyl radicals, e. g.:

n-Heptyl Sec-heptyl 2,3-dimethyl-3-perityl 2,4-dimethyl-2-pentyl 2,4-dimethyl-3-pentyl 2,2,3-trimethyl-3-butyl 3-ethyl-2-pentyl 2-methyl-2-hexyl, etc.

Octyl radicals, e. g.:

11-Oct 1 y Properiyl radicals, e. g.:

Allyl Iso-propenyl Butenyl radicals, e. g.:

n-Butenyl-i n-Bntenyl-Z n-Butenyl-3 Isc-bntenyl Pentenyl radicals, e. g.:

n-Peritenyl-l n-Pcntenyl-2 n-Pentenyl-3 Hexenyl radicals, e. g.:

n-Hexenyl-l n-Hexeny1-2, etc. 4,4-dimethyl-butenyl-2 3,4-dimethyl-butenyld, etc. Heptenyl radicals, e. g.: n-heptenyl rarefied Dec. 13,1955

Octenyl radicals, e. g.:

n-Octenyl Dilsobutenyl Nonenyl radicals, e. g.: n-noneriyl Decenyl radicals, e. g.: n-decenyl Dodecenyl radicals, c. g.:

n-Dodecenyl triisobuteuyl Alkenyl radicals having the formula Cn In-l where n is an integer from 18 to 38 inclusive, e. g. those derived from paraflln wax, mineral oils, and petrolatum (2) C ycloalipliatic radicals, for example:

Cycloalkyl radicals, e. g.:

Cyclopentyl, alkylated-cyclopeiityl, cyclohexyl, and alkylatedcyclohexyl radicals, e. g.:

Monoand poly-methyl-cycloperityl radicals Monoand poly-methyl-cyclohexyl radicals Monoand poly-ethyl-cyclohexyl radicals Monoand poly-lso-propyl-cyclohexyl radimls Monoand poly-tcrt-amyl-cyclohexyl radicals n-Octyl-cyclohexyl radicals Diisobntyl-cyclohexyl (i. c., tert-octyl"eyclohexyl) radicals Nonyl-cyclohexyl radicals Diiso-amyl-cyclohexyl radicals Lauryl-cyclohexyl radicals Cctyl-cyclohexvl radicals Naphthenyl radicals Hydroabietyl radicals Cycloalkenyl radicals, e. g.:

Cyclopentenyl, alkylated-cyclopentenyl,

alkylatcd-cyclohexenyl radicals, e. g.:

Monoand poly-methyl-cyclopentenyl radicals Monoand poly-methyl-cyclohexenyl radicals Monoand poly-ethyl-cyclohexenyl radicals Monoand poly-iso-propyl-cyclohexenyl radicals Monoand poly-tert-amyl-cyclohexenyl radicals n-Octyl-cyclohexenyl radicals Diisobutyl-cyclohexenyl radicals Nonyl-cyclohexenyl radicals Diiso-amyl-eyclohexenyl radicals Lauryl-cyclohexenyl radicals Cetyl-cyclohexenyl radicals Dehydronaplithenyl radicals Abietyl radicals (3) Aryland cycloalkyl-substituted aliphatic radicals, 101: example: (a) ghenylland alkyl-phenyl-substituted alkyl radicals, e. g.: euzy Methyl-benzyl Oapryl-benzyl Diisobutyl-benzyl Phenyl-ethyl Phenyl-propyl Phenyl-octadecyl (b) Xenyl and alkyl-xenyl-substituted alkyl radicals, e. g.:

Xenyl-methyl Capryl-xenyl-mcthyl Xenyl-ethyl Diisobutyl-xenyl-methyl (c) Naphthyland alkyl-naphthyl-substituted alkyl radicals, e. g.:

N aphthyl-methyl Teri:-amyl-naphthyl-methyl N aphthyl-ethyl Cetyl-naphthyl-ethyl Cyclohexyland alkyl-cyelohexyI-substituted alkyl radicals, e. 8.: Cyclohexyl-ethyl Methyl-cyclohexyl-ethyl Ethyl-cyclohexylethyl Cyclohexyl-propyl Tert-amyl-cyclohexyl-buty (4) Oxygen containing aliphatic and cycloaliphatic radicals, (or example:

(a) Oxygen-containing aliphatic radicals, e. g; Alkoxy-substituted allgyl radicals, e. g.:

Propoxyethyl radicals, e. g.:

n-Propoxy-ethyl Iso-propoxyethyl Butoxy-ethyl radicals, e.-g.:

n-Butoxy-ethyl Iso-bntoxy-ethyl Tert-butoxy-ethyl Octoxy-ethyl radicals, e. g.:

n-Octoxy-ethyl Diisobutoxy-ethyl Di-butoxy-propyl radicals, e. g.:

2,3-di-n-butoxy-propyl 3,3-di-iso-butoxy-propyl Di-octoxy-propyl radicals, e. g.:

3,3-di-n-octoxy-propyl 2,3-bis-(diisobutoxy)-propyl Oycloalkoxy-substituted alkyl radicals, e. g.:

Cyclohexoxy-methyi Cyclohexoxy-ethyl radicals, e. g.:

Beta-cyclohexoxy-ethyl Alpha-cyclohexoxy-ethyl Oyclohexoxy-butyl radicals, e. g.:

2(cyclohexoxy)-butyl 2,3-di-cyclohexoxy-butyl Methyl-cyclohexoxy-propyl,radicals e. g.:

Z-(o-methyl-cyclohexoxy)-pr0pyl 2-(p-methyl-cyelohexoxy)-propyl Butyl-cyclohexoxy-ethyl radicals, e. g.:

Beta-(p-tert-butyl-cyclohexoxy)ethyl Alpha-(o-sec-butyl-oyclohexoxy)ethyl Cyclopentoxy-ethyl radicals, e. g.: Alpha-cyclopentoxy-ethyi Beta-cyclopentoxy-ethyl Propyl-cyclopentoxy-znethyl radicals, e. g.:

'Iso-propyl-cyclopentoxy-methyl radicals n-Propyl-cyclopentoxy-methyl radicals cyclohexeuyl, and

(6) Aromatic radicals, including aryl radicals, unsubstituted and substituted', including monoand polyalkylated and cyclo-alkyla'ted aromatic nuclei, e. g.: p

Ethyl-phenyl Di-ethyl-phenyl Iso-propyl-phenyl n-Propyl-phenyl 'Tert-butyl-phenyl Di-tert-butyl-phenyl lso-butyl-phenyl n-Butyl-phenyl Tert-amyl-phenyl Cyclohexyl-phenyl Methyl-cyclohexyl-phenyl Capryl-phenyl Diisobutyl-phenyl Laurylhenyl Cetyl-p enyl Paraflln wax-substituted phenyl Nitro-phenyl Mono-chloro-phenyl Poly-chloro-phenyl, e. g.: dichloro-phenyl, Hydroxy phenyl Acetyl-phenyl Garbolauroxy-phenyl Lauroxy-phenyl trichloro-phcnyl Xenyl l Monoand poly-chloro-xenyl Oapryl-xenyl Phenoxy-phenyl Thiophenoxy-phenyl Diisobutyl-phenoxy-phenyl Naphthyl Monoand pcly-chloro-naphthyl Cetyl-naphthyl Anthracyl Monoand poly-chloranthracyl Phenanthryl Monoand poly-chloro-phenanthryl Lauryl-phenanthryl MO-Ph-R, where M is one equivalent of a metal (e. g. those listed under (5) above), Ph is the benzene ring, and R is a divalent allphatic radical, e. g.: p p Alkylene radicals, e. g.: Methylene Ethylene Propylene, etc. Aromatic radicals having more than one kind of substituent, e. g.: Alkyl-hydroxy-aryl radicals, e. g.:

Mono-ruethyl-hydroxy-phenyl radicals Poly-1nethyl-hydroxy-phenyl radicals, e. g.:

Di-methyl-hydroxy-phenyl radicals Tri-methyl-hydroxy-phenyl radicals Mono-ethyl-hydroxy-phenyl radicals Poly-ethyl-hydroxy-phenyl radicals Di-cthyl-hydroxy-phenyl radicals Tri-ethyl-hydroxy-phenyl radicals Mono-butyl-hydroxy-phenyl radicals, e. g.:

Tert-butyl-hydroxy-phenyl radicals Sec-butyl-hydroxy-phenyl-radicals Poly-butyl-hydroxy-phenyl radicals, e. g.: di-tert-butyl-hydroxyphenyl radicals Mono-methyl-dihydroxy-phenyl radicals Poly-mcthyl-dihydroxy-phenyl radicals, e. g.: Di-methyl-dihydroxy-phenylradicals Tri-methyl-dihydroxy-phenyl radicals Mono-propyl-hydroxy-naphthyl radicals, e. g.: mono-isopropylalpha-hydroxy-naphthyl radicals Poly-propyl-hydroxy-naphthyl radicals, e. g.:

beta-hydroxy-naphthyl radicals Alkyl-chloro-aryl radicals, e. g.:

Methyl-monochloro-phenyl radicals Methyl-polychloro-phenyl radicals e. g.: Methyl-dichlorc-phenyl radica s Methyl-trichloro-phenyl radicals Ethyl-monochloro-anthracyl radicals, e. g.:

Ethyl-monoch1oro-alpha-anthracyl radicals Triethyl-monochloro-beta-anthracyl radicals Ethyl-polychloro-anthracyl radicals, e. g.:

Ethyl-dichloro-alpha-anthracyl radicals Diethyl-trichloro-beta-anthracyl radicals Alkyl-nitro-aryl radicals, e. g.:

Methyl-nitro-phenyl radicals Dimethyl-nitro-phenyl radicals Ethyl-dinitro-phenyl radicals Butyl-nitro-naphthyl radicals, e. g.:

Tert-butyl-nitro-naphthyl radicals Sec-butyl-dinitro-naphthyl radicals Propyl-m'tro-phenanthryl radicals, e. g.:

Isopropyl-dinitro-phenanthryl radicals Di-n-propyl-dinitro-phenanthryl radicals Compounds which contain the elements of sulphur and di-n-propylphosphorus are generally quite useful as adjuvants to,

lubricating oils for the purpose of imparting extreme pressure properties or inhibiting oxidation and corrosion. The compounds which are the principal subject of this invention contain a minimum of two atoms of phosphorus and three atoms of sulphur per molecule, and possess such valuable properties as mentioned above. In addition to their usefulness in motor oils, gear oils, and similar lubricants they may also be used as metal-flotation agents, rubber accelerator activators, and pest control agents.

It is an obiect of this invention to provide a process for the manufacture of new compositions of matter. A more specific object is the preparation of anhydrides of phosphinodithioic acids from phosphinodithioic acids by means of a cheap and efiicient method. Other objects willd become apparent as the following description procee s.

These objects are accomplished according to our invention by a thermal process which involves the elimination of the elements of hydrogen sulphide from a material comprising at least one phosphinodithioic acid. The overall process is unusually simple and economical, inasmuch as no catalysts are required and the purification procedure is neither lengthy nor complicated. The reaction rate for this conversion is sufficiently fast so that the time required for batch-wise operation of the process is relatively short; generally from one-half to eight hours and more often from one to three hours. Furthermore the nature of the reaction is such that the process lends itself to a continuous operation and the process is readily adaptable to this more convenient mode of handling.

The detailed procedure consists in heating a phosphino dithioic acid at such a temperature that hydrogen sulphide gas is evolved at a reasonably constant and vigorous rate. Agitation of the reaction mixture allows better temperature control and a more uniform reaction rate, and as a consequence of these, a higher yield of product, although the rapid evolution of hydrogen sulphide itself often provides sufficient agitation within the reaction mixture to give satisfactory results. When the evolution of hydrogen sulphide has become negligible the reaction may be considered, for the purposes of this invention, to be at an end. At this point the product mixture usually is a dark green, viscous liquid with a slight, not unpleasant odor. After washing with an alcohol it may, in most instances, be crystallized from a hot alcoholic solution. The product obtained from this procedure is sufirciently pure for the uses mentioned previously. Further purification, although generally unnecessary for the purposes of this invention, may be effected by recrystallization from the same or difierent alcohols.

Theprogress of the reaction may be observed by periodic determination of the relative acidity of the reaction mixture. Thus, the overall conversion of a phosphinodithioic acid to the corresponding anhydride is marked by the disappearance of acid groups and may be represented by the following equation:

gen sulfide is so slight as to be negligible. Thus in the ordinary practice of this invention the process is allowed to proceed until the acid number of the product mixture has decreased substantially, preferably to an approximately constant value. The temperatures which may be employed for the preparation of phosphinodithioic acid anhydrides cover a fairly wide range. At-temperatures as low as C. there is observed an appreciable drop in the acid number of diphenylphosphinodithioic acid; e. g. a drop from an acid number of 203 to a value of 187 after 18 hours. Higher temperatures, however,

allow a much faster reaction and in most cases it is desirable to employ temperatures of not less than C.

Lower temperatures than 130 C. may be used, but the lethargy of a reaction run at such a low temperature en er he P =$1L QQ 10 I Q Th urns: l m Q semesters q crn ag nl by the vi la- 9a .of til? 'ea t qn bu s9-b the pro l ms, .of dc pm si i n- Thus in n PI,. ..11 involv n d p en p es hin clithiloic.acidv at. 2 5il) C. the acid number was observedto drop from '203 to 69 within the first hour of such heating n o r se ea t r to -13 d ring the s cond hour an thence to 7.9 during the third Ihour-at this temperature.

riseinthe acid number-is interpreted ,tornean that acidic products ,of'decompositi'on are being formed at a ,rate than phosphinodithioicaeidis-being converted irr s o d n a hydridchwa uc si cr ab e ii aIe hatWhil -ZS .C-is a er a i fa ryemrsr i urs for t e qa of h s n c i h r em erat res than.25.Q? -C. willbeincreasingly less satisfacto iy. vIn general then .it. can beseen that temperatures within the lIlQfiQfil-MJSQ" .Cvare satisfactoryforthe thermal conversionof phosphinodithioic acids'to phosphinodithioic sid a ide The'acids which "are rused as raw materialsare commonly prepared by use of the G fi nard reagent, as h wn br ew ZHiO iniv x R sa znarssn 2Mg QIEQX MGS MgXfl The. aliphatic, phosphinodithioic. acids. are; prepared via. the aboyescheme in :refluxing ethyl ether solution Whereas the aromatic phosphinodithioic acids are prepared .at somewhat highertemperatures, -'usually. about 100 Alternatively theseacids may insorne cases'be prepared more conveniently by. sulfurizing secondary phosphines, as illustratedby the following-equation:

The ,.procedure.for.carrying out the above, indicated reaction consists. simply. in Warming the particular phosphine with elemental sulfur inan inert atmosphere.

Another method for]preparing the 'phosphinodithioic aeidsQis setlforth in the copjending application ofQMill'er et 'aL, Serial No. 406,323, .for 'fQrganic 'Bhosphinodithioic Acid Compounds and ,Methods' for Preparing Same,,.ow ned.by.the-same,asSi nee.

'It is apparent that the scope of the'inventionincludes, the preparation not only of symmetrical molecules such as resulted from the use of pure phosphinodithioic acids, but also'of unsymmetricalanhydride molecules which resulted from the'use-of a mixture of two or more phosphinodithioic acids. In the latter case, if :a mixture of two phosphinodithioic acids, A and B, is treated according to the practice of this invention the product mixture is apt to contain three distinct products, viz. the anhydride which contains two A residues, the anhydride which B e id an the nhy jd h c n- .Pth' an l r s d e n a B- es e n ra on qn mr es a o he e o hcsp in c ac ds which. w ta ni simi a r an i 1$, While not readily available are nevertheless so lth b qad c ass of p cs'phi od t b s c ar f hc subi ct of s. n en i S ecifi ex if. this type of compound include; ethylmethylphosp iuqli h i c d i892 qpy m th p n d t ic'a d, PtYli nrqp lphdsnh n dit i i d. cyclcp r t c h lph srh i dit i a d cy oh x l b ty rh p n i thioi'c acid, 'c yclohexylcyclopentylphosphinodithioic acid, mflzy hsnvlrhcs hi dd qic arid, p e ltn-p r r p yiqsiih /i yditl i i a id. s qp n ph i p s h rlqd 8 e road eat rss 5 this ,invcn isn havin been. s t forth, :the :followingexamples :are now-presented ito clarify some of the details thereof:

Example 1 A sample of diphenylphosphinodithioic.acid, weighing 250 grams (1.0 mole) was warmed with agitation-'10 -1 fZ0 C. and these conditions were maintainedtqr aperiodof two hours. During this time the acid numberdropgcd from 210 to 92. The dark green reactionproduct'was allowed to cool to approximately room temperature, whereupon milliliters of cold methanol .was added and the resultant mixture was stirred for afew seconds. The dark syrupy liquid became partially crystalline, .and upon decanting the methanol away and washing with a second 100-milliliter portion of methanol theenti remass crystallized. This product was subsequently re cry'al lized from 500 milliliters of isopropanolto ;yi,e1ld"l 98 grams (85.0 percent of the theory) ofa white e 'lystalline product which melted at -1 10 C. Afsar'nplepfthis product, diphenylphosphinodithioic acid anhydride, crystallized twice more from isopropariol meit aat 1; 135- 1l6.5 C.

Example 2 The procedure of Example 1 was repeated ,at2 5Q--,C. for one hour. The correspondingyieldotproduct melting at 106-ll0 C., was 191 grams (82.0 perccilt offthe theory).

The procedure of Example 1 wasrepeatedat 1 30" C. for five hours. The corresponding yield of product, melting at 100-107 C., was 140.5 grams (60 3 percent of :the theory) Having described my invention andfurnished specific examples thereof, no undue limitations or restrictions should be placed on thejscqpe of myinYcntion-except to the extent as defined in the appended. claims.

Other modes of applyingtheprin'ciple'of the.1' nvention may be employed, change being-made as regards the details described, provided'the features. sifltcdfinany of the following claims ,or th'eequivalent of suchkbe employed.

"We therefore particularly point out and, distinctly claim as our invention; I

1. The process 'for-prcparing anhydrides of phosphinodithi j acidswhich c prises'hcating-at' lcastcnephosphinodithioic acid havrgithe structure phosphinodithioic acids which comprises'heating at least one phosphinodit ioic. acid. having.thelstructure wherein'R and R are'the same or diflerent non-functional organic radicals attached to phosphorus through a carbon atom, .within a temperature range of, from about C. to about 250 C. until the acid number of the product :mixture has decreased substantially.

The process of claim 2 further characterizedfin that the phosphinodithioic acid is heated for a periodotf I from about {/2 to about 8 hours.

1 P Q$P of cla m. 2 r her. chara ter zed. in that,

Jthe organic radicals are hydrocarbon radicals.

5. The process of claim 2 further characterized in that References Cited in the file of this patent the organic radicals are cyclic hydrocarbon radicals. UNITED STATES PATENTS 6. The process of claim 2 further characterized in that 2,198,915 M ac Me 6 30, 1940 the organic radicals are aryl radlcals.

7. The process of claim 2 further characterized in that 5 OTHER REFERENCES the organic radicals are phenyl radicals. Kosolapoff et al.: 73 J. A. C. S., 4101. 

1. THE PROCESS FOR PREPARING ANHYDRIDES OF PHOSPHIONDITHIOIC ACIDS WHICH COMPRISES HEATING AT LEAST ONE PHOSPHINODITHIOIC ACID HAVING THE STRUCTURE 